Internal combustion engines are conventionally equipped with a variety of fluid tanks, for example a fuel tank or an urea tank containing urea solution used in the exhaust gas treatment system, for which it is desirable to monitor to some degree the level of the fluid within. Continuous fluid level sensors have widely been used for detecting the level of fluid in a tank. They work by continuously measuring a level within a specified range and determining the exact amount of fluid in the tank as a function of the measured level. Unfortunately these sensors are relatively expensive. As alternative to continuous sensors, discrete level sensors could also be used. Discrete level sensors provide information on the level of fluid in the tank by simply indicating whether the fluid in the tank is above or below predetermined level threshold values. Discrete level sensors are therefore less precise since they are unable to detect the precise level of fluid between two level threshold values. Also when used in internal combustion engines they present additional problems. During transitory driving states of the vehicle, i.e., for example, during acceleration or deceleration, discrete level sensors provide level indications which are often misleading. In those situations the fluid in the tank is sloshed around and the level threshold values are randomly exceeded so that the sensor provides conflicting information regarding the actual level of the fluid in the tank. This is even truer when the discrete level sensors are used, for example, to detect the level of urea in urea tanks. Such tanks normally have a relatively flat and wide parallelepiped shape and small movements of the vehicle are enough to cause the fluid to slosh in the tank and to randomly exceed or fall below various threshold level values.
In view of the above, it is at least one object of an embodiment herein to provide a method to determine in a substantially precise way the fluid level in a fluid tank equipped with a discrete level sensor.
Another object of an embodiment herein is to provide a method for determining a fluid level which is substantially reliable even in transitory driving conditions.
Another object of an embodiment herein is to achieve the above mentioned objects in a simple, rational and inexpensive way without using complex devices and by taking advantage of the computational capabilities of an Electronic Control Unit (ECU) of the vehicle.
These objects are achieved by a method, by an engine, by a computer program and computer program product, by an electromagnetic signal, and by an automotive system having the features recited in the independent claims. In addition, other objects, desirable features and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.